This invention involves a chain guide rail for guiding a chain between two chain wheels, having a rail body made of resinous plastic and a guide rail connected to it, which is also made of plastic, with a running groove to receive the chain. In addition to its guide function, the chain guide rail can also function for tensioning or rerouting the chain. Rails of this type are especially necessary if chains do not run in straight lines between chain wheels, but instead must be deflected out of their straight-line progression, because, for example, structural components are in the way. This type of deflection of the chain can also result in an additional tensioning of the chain. Finally, rails of this type represent a simple possibility for guiding chains and can thus also help to prevent chains from jumping off of chain wheels.
In order to enable as easy and simple a gliding or sliding of a chain in a running groove of a rail as possible, and to keep frictional losses low, rails of this type are generally manufactured completely of plastic. The rail itself can be constructed in different ways. Thus, it can have a rectangular cross-section, whose width substantially corresponds to a width of the running groove. It can, however, also include only a narrow web which supports a guide rail that contains the running groove. The rail then has a cross-section in the form of a T or double T profile, with one of the cross-beams functioning as a guide rail. Reinforcement ribs can also be provided.
Use of rails of plastic has the disadvantage that the plastic is not able to handle high loads acting on the chain guide rail by the chain that slides on it. This is true particularly when the rail causes, in addition to having its guide function, also a deflection of the chain from of its normal running plane or tensions in the chain. A plastic rail can only support limited high forces and might be deformed--possibly to a breaking point--under an acting stress.
It is therefore also known to construct such a rail as a cast metal part and merely mount onto the cast part a plastic slide lining, which reduces frictional forces. Disadvantageous in this embodiment are the relatively high costs for the cast part. Furthermore, there is a problem of anchoring the slide lining permanently and securely to the metallic rail body at a reasonable price.
A purpose of the invention is therefore to provide a chain guide rail which can be manufactured in a cost effective manner and, nevertheless, can withstand high stresses of a chain that runs over it.